The beforeinstallprompt event is fired by the browser when a Progressive Web App (PWA) meets all installation criteria. It signals that the browser is ready to show the native install prompt to the user. Developers can intercept this event using e.preventDefault() and trigger the prompt later, allowing custom install flows. This event is crucial for PWA adoption as it indicates the app is installable.

Common reasons include: (1) Site not served over HTTPS (localhost is exempt), (2) Missing or invalid Web App Manifest, (3) No Service Worker registered, (4) Manifest lacks required fields (name, icons ≥192px, start_url, display), (5) User has already installed the PWA, (6) User previously dismissed the prompt (Chrome may throttle re-prompts), (7) Browser doesn't support PWA installation (e.g., Firefox desktop). Use this checker to identify exactly which requirement is failing.

Chrome requires: HTTPS connection, a valid Web App Manifest with at least name (or short_name), icons array containing a 192x192 PNG icon and a 512x512 maskable icon, start_url, and display set to standalone, fullscreen, or minimal-ui. Additionally, a Service Worker must be registered and active. The user must also have sufficient engagement with the site (varies by browser).

Use this tool to see real-time status. In your code, add: window.addEventListener('beforeinstallprompt', (e) => { console.log('Install prompt available!', e); deferredPrompt = e; }); Also check Chrome DevTools under Application → Manifest for manifest validation and Application → Service Workers for SW status. The Lighthouse audit can also identify PWA issues automatically.

Yes! Chrome allows PWA installation on localhost and 127.0.0.1 without HTTPS. You still need a valid manifest and service worker. Use npx serve or python -m http.server for quick local testing. Chrome also provides a "Add to Home screen" option in DevTools under Application → Manifest for manual testing. For Safari, you need a Mac with Xcode to test iOS PWA installation.

Chrome (desktop & Android, v67+), Edge (v79+), Opera (v54+), and Samsung Internet fully support beforeinstallprompt. Safari on iOS/iPadOS uses a different mechanism (WebKit's apple-mobile-web-app-capable meta tag) and does not fire this event. Firefox does not support PWA installation on desktop. Firefox for Android has limited support. Always implement a fallback install flow for unsupported browsers.

A Web App Manifest is a JSON file that tells the browser how your PWA should behave when installed. Required fields: name or short_name (app name), icons (array with at least one 192x192 and one 512x512 icon), start_url (the URL to load when the app launches), and display (should be standalone for a native-like experience). Recommended: theme_color, background_color, description, scope, and categories.

If a user dismisses the native install prompt, Chrome applies a cooldown period before it will fire beforeinstallprompt again. This period is typically around 90 days for the mini-infobar and 3 months for the full prompt, though the exact duration is not publicly documented and may change. To reset during development, clear site data in Chrome or use an incognito window. On Android, clearing Chrome's storage for the site can also reset this.